Sebum or skin oil is produced in the sebaceous glands located in the pilosebaceous apparatus of the skin and reaches the skin surface through ducts of the hair follicles. The presence of excessive amounts of sebum on the skin surface often results in an unattractive cosmetic condition commonly known as "oily skin." Depending on the regions of sebaceous gland activity and the level of sebum secretion, the population is often classified by skin type, e.g., dry, normal, oily, combined dry/normal, combined dry/oily, or combined normal/oily skin (the latter two classes hereinafter alternatively referred to as "combination skin").
Persons having an oily skin type or a combination skin type typically manifest an oily and/or shiny skin appearance between cleansings. Following initial cleansing of the skin, this oily or shiny appearance generally increases as the day progresses. In order to avoid such appearance, individuals must throughout the day either cleanse the skin, blot the skin, apply oil absorbing powders to the skin, or take some other measure to minimize the appearance of oil or shine. Therefore, it has been desired in the art to provide topical compositions which reduce sebum synthesis by the sebaceous glands and minimize the appearance of oil and/or shine on the skin, especially oily or combination skin.
Furthermore, in the field of cosmetic or make-up compositions, several topical compositions which are said to be designed for controlling oily and/or shiny skin are known in the art. For example, facial moisturizers and make-up said to have such property are known. However, an oily or a combination skin type presents a particular challenge to the formulation of make-up intended for facial use, including foundations. As oil accumulates on the facial skin of such individuals, oil breakthrough occurs. In other words, the make-up fails to sufficiently mask the oil such that an oily or shiny skin appearance results. As a result, the coverage and wear resistance of the make-up tends to be reduced. It would be desirable to provide a make-up composition that maintains a high degree of coverage and wear resistance after application to all skin types, including oily and combination skin, preferably substantially as originally applied.
While certain formulations have been designed in an attempt to control the oily and/or shiny appearance of skin, there remains a need to provide improved topical compositions for reducing sebum synthesis by the sebaceous glands and minimizing the appearance of skin oil and/or shine. In addition to minimizing oil and/or shine, such compositions should not unacceptably discolor the skin. Therefore, there is a particular need to provide improved skin care compositions and make-up which (i) reduces sebum synthesis by the sebaceous glands, (ii) minimizes the appearance of skin oil and/or shine, (iii) provides and maintains an even (i.e., uniform coverage) complexion and acceptable skin tone for extended periods after application, and/or (iv) which has extended wear resistance after application.
Dehydroacetic acid and its pharmaceutically acceptable salts have heretofore been used as preservatives, antimicrobial agents, and bactericides in cosmetic formulations, food packaging and veterinary drugs. These utilities and many others are further described in the Final Report on the Safety Assessment of Sodium Dehydroacetate and Dehydroacetic Acid, Journal of the American College of Toxicology, Vol. 4, No. 3, pp. 123-159 (1985).
It has surprisingly been found that dehydroacetic acid and its pharmaceutically acceptable salts are useful when topically applied for inhibiting sebaceous gland activity. Since the sebaceous gland is a principal source of oil on mammalian skin and scalp, a primary benefit of controlling sebaceous gland activity (e.g., sebum secretion) includes a reduction in the level of oil found in skin and hair. As a result, dehydroacetic acid is useful for regulating the appearance of oily and/or shiny skin, including oily and combination skin. It has also surprisingly been found that topical compositions containing these compounds in the form of a facial make-up composition minimize the appearance of skin oil and/or shine, provide and maintain substantially uniform coverage and an acceptable skin tone for extended periods after application, and/or have extended wear resistance after application.
Because of the ability of dehydroacetic acid to control sebaceous gland activity, it has also been found to be useful in treating acne and related skin disorders in mammalian skin and scalp, such as, eczema, seborrhea, impetigo, psoriasis, rosacea.
It is an object of the present invention to provide topical compositions for inhibiting sebaceous gland activity which results in effectively regulating the oily and/or shiny appearance of mammalian skin, especially facial skin. It is a further object of this invention to provide such topical compositions which regulate the appearance of oily and/or shiny mammalian skin, provide and maintain substantially uniform coverage for extended periods after application to the skin, provide and maintain an acceptable skin tone for extended periods after application to the skin, and/or have extended wear resistance after application to the skin. Another object of the present invention is to provide methods of regulating the appearance of oily and/or shiny mammalian skin and methods of reducing sebum synthesis by the pilosebaceous glands.
It is a further object of the present invention to provide topical compositions for treatment of acne and related skin disorders in mammalian skin and scalp.
Other objects of the subject invention will be apparent from the disclosure which follows.